During the tenth year of support, 21 professional medical scientists and 14 physiology graduate students reported progress upon 144 separate research projects, including 75 publications. These reports emanated from Program-project HL08682 in which cardiovascular research deals with: 1) Cardiodynamic regulation, 2) CNS regulation of cardiopulmonary mechanisms, 3) Cardiac metabolism, 4) Physiological control systems and temperature regulation, 5) Mechanical properties of blood vessels, 6) Cardiovascular studies of mammalian hibernators, 7) Neural and vascular feedbacks in endocrinology, 8) Spinal regulation of vasomotor and sudomotor outflows, 9) Reinnervation of the transplanted heart, and 10) Histochemical and ultra-structural study of cardiac innervation. Transection and reanastomis of the atria produces complete cardiac denervation without interruption of innervation of other thoracic organs. Careful surgical disection of local neural projections permits selective denervation of individual portions of the heart. Electrical excitation of small branches of the thoracic vagus revealed specific distribution of parasympathetic fibers to localized regions of the heart. Thus, as previously shown in the sympathetic distributions, separate stimulation of these branches often elicits evidences of asynchrony and dysrhythmia as well as unequal inotropic responses. The participation of both contractile and elastic elements in smooth muscle of the carotid artery has been investigated and described during isometric and isotonic contraction. The discharge patterns of individual respiratory cells and their interactions within the CNS to produce alterations in respiratory rhythmicity and baroreceptor afferents have been examined. The participation of the liver and the reticuloendothelial system in the development of hemodynamic and endotoxin shock has been pursued very vigorously. A colony of hibernating ground squirrels has been maintained on a twelve month basis, and the hearts, blood, and other tissues from such animals studied extensively. The location and functional properties of cardiac sympathetic and vasomotor pathways have been documented within the cervico-thoracic spinal cord.